Combustion of Volatile Organic Compounds to CO2 and H2O with Low NOx Formation

ABSTRACT

A process of combusting a gaseous volatile organic compound over a modified alumina catalyst at a temperature below 5° C. while exothermically producing CO 2  and H 2 O at a temperature from about 5° C. to about 1100° C.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional application which claims the benefit of and priority to U.S. Provisional Application Ser. No. 61/502,142 filed Jun. 28, 2011, entitled “Combustion of Volatile Organic Compounds to CO2 and H2O with Low NOx Formation,” which is hereby incorporated by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

None.

FIELD OF THE INVENTION

A process of combusting gaseous volatile organic compounds with low NOx formation.

BACKGROUND OF THE INVENTION

The preheating of gases and/or feedstocks in a refinery (or other plant) is an important step in overall plant operations. Most plant processes operate at an elevated temperature that requires preheating the gases and/or feedstocks. The gases and/or feedstocks are generally preheated combusting a fuel gas in a furnace and passing the gases and/or feedstocks through heat exchanger tubes in the heated portion of the furnace. Conventional flame combustion methods have the disadvantages of NO_(x) formation at typical flame temperatures and inefficient heat transfer between the flame and the heat exchanger tubes.

Accordingly, a preheating method is needed to reduce the formation of NO_(x) and to improve the heat transfer between the flame and the heat exchanger tubes.

SUMMARY OF THE INVENTION

A process of combusting a gaseous volatile organic compound over a modified alumina catalyst at a temperature below 5° C. while exothermically producing CO₂ and H₂O at a temperature from about 5° C. to about 1100° C.

In an alternate embodiment a process of combusting a gaseous volatile organic compound selected from a group consisting of: methanol, ethanol, propanol, n-heptane, gasoline, crude oil, n-C₁-C₆ paraffins, i-butanol, n-hexane, toluene, acetone, hydrogen and combinations thereof in an oxygen containing gas such as air, over a modified alumina catalyst at a temperature below 5° C. This is followed by exothermically producing CO₂ and H₂O at a temperature from about 5° C. to about 1100° C. while not substantially forming NOx. In this embodiment the modified alumina catalyst comprises from about 0.005 wt % to about 5 wt % Pt and a MgO modified alpha-alumina cloth support and/or a gamma alumina powder support.

In yet another embodiment a process discloses using a heat exchanger with a thin layer of a modified alumina catalyst bed in contact with the heat exchanger and sprayed or coated catalyst alumina slurry on heat exchanger. A gaseous volatile organic compound is combusted over the modified alumina catalyst at a temperature below 5° C. This is followed by exothermically producing CO₂ and H₂O while simultaneously raising the temperature of the heat exchanger from about 5° C. to about 1100° C.

In an alternate embodiment a process discloses using a heat exchanger with a thin layer of a modified alumina catalyst bed in contact with the heat exchanger and sprayed or coated catalyst containing alumina slurry on heat exchanger. A gaseous volatile organic compound selected from a group consisting of: methanol, ethanol, propanol, n-heptane, gasoline, crude oil, n-C₁-C₆ paraffins, i-butanol, n-hexane, toluene, acetone, hydrogen and combinations thereof in oxygen containing gas such as air, is then combusted over a modified alumina catalyst at a temperature below 5° C. This is followed by exothermically producing CO₂ and H₂O at a temperature from about 5° C. to about 1100° C. while not substantially forming NOx. In this embodiment the modified alumina catalyst comprises from about 0.005 wt % to about 5 wt % Pt and a MgO modified alpha-alumina cloth support and/or a gamma alumina support.

These and other objects, features, and advantages will become apparent as reference is made to the following detailed description, preferred embodiments, and examples, given for the purpose of disclosure, and taken in conjunction with the accompanying drawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of the nature and objects of the present inventions, reference should be made to the following detailed disclosure, taken in conjunction with the accompanying drawings, in which like parts are given like reference numerals, and wherein:

FIG. 1 a is a schematic of a heat exchanger;

FIG. 1 b is a schematic of a catalyst on a single heat exchanger-style tube-catalyst-shell heater from FIG. 1 a;

FIG. 2 is a schematic of an apparatus for evaluation of a single heat exchanger-style catalyst tube-shell heater;

FIG. 3 is a chart of data for combustion of methane in air over a methanol combustion catalyst in a heat exchanger; and

FIG. 4 is a chart of data for combustion of methane in air over a diluted methanol combustion catalyst in a heat exchanger.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTIONS

The following detailed description of various embodiments of the present embodiment references the accompanying drawings, which illustrate specific embodiments in which the embodiment can be practiced. While the illustrative embodiments of the invention have been described with particularity, it will be understood that various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the spirit and scope of the embodiment. Accordingly, it is not intended that the scope of the claims appended hereto to be limited to the examples and descriptions set forth herein but rather that the claims be construed as encompassing all the features of patentable novelty which reside in the present embodiment, including all features which would be treated as equivalents thereof by those skilled in the art to which the embodiment pertains. Therefore, the scope of the present embodiment is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled.

A process of combusting a gaseous volatile organic compound over a modified alumina catalyst at a temperature below 5° C. while exothermically producing CO₂ and H₂O at a temperature from about 5° C. to about 1100° C.

In one embodiment gaseous volatile organic compounds can contain methanol, ethanol, propanol, n-heptane, gasoline, crude oil, n-C₁-C₆ paraffins, i-butanol, n-hexane, toluene, acetone, hydrogen or any combinations of the above in an oxygen containing gas such as air. One skilled in the art would be able to determine the appropriate flow rate of the different gaseous volatile organic compounds by balancing the rate of total combustion versus the rate of undesirable products produced. In one embodiment there is a complete combustion of the volatile organic compounds to produce CO₂ and H₂O.

As an example, the chemical reaction for complete combustion of methane in oxygen is

CH₄+2O₂→CO₂+2H₂O+heat,

and the reaction for complete combustion of methane in air is

CH₄+2O₂+7.52N₂→CO₂+2H₂O+7.52N₂+heat.

The modified alumina catalyst can be modified by any group 8, 9, 10, 11 or 12 metal. An example of a metal that has been shown to be compatible is platinum. The modified alumina catalysts were prepared using a conventional impregnation methods followed by calcinations. The amount of metal impregnated onto the modified alumina catalyst can from about 0.005 wt % to about 5 wt %, 0.01 wt % to about 5 wt % or even 0.01 wt % to about 4 wt %. The modified alumina catalyst can also be modified by incorporating a modified alpha-alumina cloth or a gamma alumina support. An example of an alpha-alumina cloth or a gamma alumina support that is capable of being incorporated onto the modified alumina catalyst is a MgO modified alpha-alumina cloth and/or a gamma alumina support. In one embodiment the modified alumina catalyst is modified by both platinum and a MgO modified alpha-alumina cloth support or a gamma alumina support.

Unlike conventional volatile organic compound combustion methods the temperature of the gaseous volatile organic compound does not need to be extensively heated in our current process. The catalytic reaction is capable of reacting at temperatures below 150° C., 100° C., or even below 5° C. under certain conditions. When the gaseous volatile organic compound reacts on the modified alumina catalyst bed it produces an exothermic reaction to produce CO₂ and H₂O.

Under conventional volatile organic compound combustion methods, excessive amounts of NOx are produced. This is partially due to the high temperatures in which their conventional reactions occur at. In our current embodiments, due to the selective nature of our modified alumina catalyst bed, the exothermic reaction does not achieve a temperature sufficient to generate significant quantities of NOx gases. In one embodiment the exothermic reactions occurs from below 5° C. to about 1100° C., 100° C. to about 1100° C. 500° C. to about 1100° C., 700° C. to about 1100° C. or even 800° C. to about 1100° C.

In one embodiment the exothermic reaction of the gaseous volatile organic compounds are able to transfer heat to a heat exchanger. In such an embodiment a thin layer of a modified alumina catalyst bed is in contact with the heat exchanger. When the gaseous volatile organic compound flows over the modified alumina catalyst the exothermic reaction transfers the heat to the heat exchanger. There are a variety of commercial uses for such a reaction to occur, such as a pre-heater for high temperature reactors or for generating steam.

An improved heater-exchanger style preheater with a plurality of catalyst beds is shown in FIGS. 1 a and 1 b. As shown in FIG. 1 a, the heat exchanger 100 comprises an inlet 110 for a fuel gas mixture with volatile organic compounds and oxygen containing gas such as air and an outlet 115 for flue gas (e.g., CO₂, H₂, CO, N₂). A plurality of heat exchanger tubes 105 pass through a heated portion of the heat exchanger 120. Each of the heat exchanger tubes 105 has an inlet 110 for cool gas and/or feedstock, and an outlet 115 for hot gas and/or feedstock.

As shown in FIG. 1 b a thin layer of a modified alumina catalyst 135 is in contact with a heat exchanger tube 105. The modified alumina catalyst wraps or sprayed around the heat exchanger tube 105 to form a catalyst bed 135 in the annulus between the heat exchanger tube 105 (i.e., inner tube) and a shell 140 (i.e., outer tube). The catalyst 135 formed greatly improves the heat exchanger capabilities.

In an embodiment, a fuel gas/volatile organic compound and oxygen containing gas mixture is initially passed over the catalyst-covered heat exchanger tubes in the heat exchanger-style furnace. The volatile organic compounds combust over the catalyst, and raises the catalyst temperature to a combustion temperature that supports combustion of the coexisting fuel gas. Experimental evidence has shown that this combustion temperature is generally about 800° C., and that, at this temperature, NO_(x) does not form from the nitrogen in the air. Once the catalyst bed temperature reaches the combustion temperature for the fuel gas and the combustion reaction sustains itself, the volatile organic compound supply may be shut off from the feed.

In an alternate embodiment the catalyst does not cover the outside of the heat exchanger but instead coat the inside of the heat exchanger.

An experimental apparatus for evaluation of a single heat exchanger-style catalyst tube-shell heater is shown in FIG. 2. As shown in FIG. 2, the heat exchanger-style preheater 200 comprises an inlet 240 for a fuel gas mixture (e.g., fuel gas and volatile organic compounds) and an outlet 265 for flue gas (e.g., CO₂, H₂O, CO, N₂). A single heat exchanger tube 205 (i.e., inner tube) passed through a heated portion of the heat exchanger-style, catalyst tube-shell heater 255 (i.e., outer tube). Both inner 205 and outer 255 tubes were made of stainless steel. A catalytic combustion catalyst was packed in the inner tube 205 to form a catalyst bed 250.

Air was used as a cooling medium for the inner tube 205 (and catalyst bed 250), and was controlled using a flow meter. The cooling air entered the outer tube at one end 245, passed through the annulus between the inner 205 and outer 255 tubes to remove some of the heat generated by the combustion reaction, and exited the other end 260.

A fuel gas mixture was blended in-situ by flowing fuel gas 210, air 215 and nitrogen 220 into one end of the inner tube 205. The mass flow rate of the fuel gas was controlled by a mass flow controller 225, the mass flow rate of the air was controlled by a mass flow controller 230, and the mass flow rate of the nitrogen was controlled by a mass flow controller 235. The fuel gas mixture (i.e., methane and air) entered the inner tube 205 at one end, combusted over the catalyst bed 250, and the flue gas (e.g., CO₂, H₂O, CO, N₂) exited the other end.

A portion 270 of the flue gas was diverted to a NO_(x) Analyzer for analysis of NO_(x), and a portion 275 of the flue gas was diverted to a gas chromatograph for a compositional analysis including CO. A backpressure element (not shown) was used to create a back pressure so that the portion of the flue gas would be diverted to the analyzers. The NO_(x) analyzer was used to detect NO_(x), and to determine the NO_(x) concentration in the flue gas. The gas chromatograph was used to detect CO and other components, and to determine their concentrations in the flue gas.

Three methods may be used to initiate a combustion reaction. One method is to add methanol or ethanol vapor to the fuel gas mixture. The methanol combusts (i.e., reacts with oxygen) on the catalyst bed 135, 250, and raises the catalyst bed 135, 250 temperature to a combustion temperature that supports combustion of the coexisting fuel gas. Once the catalyst bed 135, 250 temperature reaches the combustion temperature for the fuel gas and the combustion reaction sustains itself, the methanol supply may be shut off from the feed if desired.

A second method is to add hydrogen gas to the fuel gas mixture. The hydrogen combusts (i.e., reacts with oxygen) on the catalyst bed 135, 250, and raises the catalyst bed 135, 250 temperature to a combustion temperature that supports combustion of the coexisting fuel gas mixture. The hydrogen combustion on the catalyst bed 135, 250 may be spontaneous. Once the catalyst bed 135, 250 temperatures reach the combustion temperature for the fuel gas and the combustion reaction sustains itself, the hydrogen supply may be shut off from the feed if desired.

A third method is to preheat the fuel gas mixture to the temperature that supports combustion of the fuel gas mixture.

Catalysts used for the experiments were platinum (Pt) supported on magnesium modified aluminum oxide (Al₂O₃). The catalysts were prepared using a conventional impregnation method followed by calcinations. The catalyst compositions are shown in Table 1.

TABLE 1 Catalyst Compositions Catalyst Pt (wt %) Mg (wt %) Support Size (mesh) 1 4 3 Al₂O₃ 20 to 30 2¹ 4 3 Al₂O₃ 20 to 30 3 1 3 Al₂O₃ 20 to 30 ¹The 4 wt % Pt catalyst was diluted with an inert catalyst carrier material (e.g., silicon carbide (SiC) support).

Example 1 4 wt % Pt/3 wt % Mg/Al₂O₃

In Example 1, 4 wt % platinum (Pt) catalyst was evaluated for combustion of methane in air. The length of the catalyst bed 250 was 1.375 inches. The fuel gas mixture feed was 3.3 standard liters per minute (SLPM), the fuel gas was methane, and the ratio of air to methane was 10:1, at which the oxygen content in the air is slightly greater than the amount that is required for complete combustion of methane.

Air 245 was used as a cooling medium for the inner tube 205 (and catalyst bed 250). The flow rate of the cooling air was between 25 to 100 standard cubic feet per hour (SCFH). The cooling air was used to cool the inner tube 205 (and catalyst bed 250) so that the effects of combustion temperature on NO_(x) formation could be quantitatively determined.

The experimental data for combustion of methane in air over combustion catalyst 1 in a heat exchanger-style catalyst tube-shell heater is shown in FIG. 3. As shown in FIG. 3, the data indicates that the temperatures (i.e., inlet temperature of the catalyst bed 250, outside surface temperature of the inner tube 205, outlet temperature of the cooling air 260) decreased with increasing cooling air flow except the outlet temperature of the catalyst bed 250. The outlet temperature of the catalyst bed 250 decreased with increasing cooling air flow up to 80 SCFH, and then, above this flow rate, the outlet temperature increased. This increase may be attributed to a reaction zone shifting or extending closer to the end of the catalyst bed 250 than the prior position.

NO_(x) formation varies with reactor temperature, and generally NO_(x) formation tends to decrease with decreasing temperature. NO_(x) concentration in the flue gas was about 38 ppm at an outside surface temperature of the inner tube 205 of about 655° C., and about 1 ppm at an outside surface temperature of about 254° C. For a NO_(x) concentration of about 1 ppm, outlet temperature of the catalyst bed was about 640° C. An upper limit for the outlet temperature of the catalyst bed was about 716° C.

During the experiment, no carbon monoxide was detected in the flue gas, and, therefore, all of the methane was combusted.

Example 2 4 wt % Pt/3 wt % Mg/Al₂O₃ Diluted with Inert Catalyst Carrier Material

In Example 2, 4 wt % Pt catalyst was diluted with an inert catalyst carrier material (e.g., SiC support). The diluted catalyst was evaluated for combustion of methane in air. The length of the diluted catalyst bed 250 was 1.375 inches. Similar to Example 1, the fuel gas mixture (i.e., methane and air) feed was 3.3 SLPM, the fuel gas was methane, and the ratio of air to methane was 10:1.

Air 245 was used as a cooling medium for the inner tube 205 (and catalyst bed 250). The flow rate of the cooling air was between 50 to 65 SCFH. The cooling air was used to cool the inner tube 205 (and catalyst bed 250) so that the effects of combustion temperature on NO_(x) formation could be quantitatively determined.

A chart of experimental data for combustion of methane in air over a diluted combustion catalyst in a heat exchanger-style catalyst tube-shell heater is shown in FIG. 4. As shown in FIG. 4, the highest observed NO_(x) concentration was about 6 ppm. At this NO_(x) concentration, the outlet temperature of the catalyst bed 250 was about 678° C. and the outside surface temperature of the inner tube 205 was about 523° C. During the experiment, the NO_(x) concentration ranged from about 0 to 6 ppm, the outlet temperature of the catalyst bed 250 ranged from about 647 to 678° C., and the outside surface temperature of the inner tube 205 ranged from about 342 to 523° C.

No carbon monoxide was detected in the flue gas, and, therefore, all of the methane was combusted.

Example 3 1 wt % Pt/3 wt % Mg/Al₂O₃

In Example 3, the catalyst loading was reduced from 4 to 1 wt % Pt to spread the combustion reaction across the catalyst bed. The combustion reaction on the 4 wt % Pt catalyst occurred on the front of the bed. The 1 wt % Pt catalyst was evaluated for combustion of methane in air. Reducing the catalyst loading requires a longer residence time on the catalyst for reaction thus extending the hot zone of the catalyst bed. This provide for a larger surface of tube 205 that is heated. Accordingly, the 1 wt % Pt catalyst bed 250 was 1.5 inches, which is slightly longer than the 1.375 inch bed used in Examples 1 and 2. Similar to Examples 1 and 2, the fuel gas mixture (i.e., methane and air) feed was 3.3 SLPM, the fuel gas was methane, and the ratio of air to methane was 10:1.

The experiment was carried out without air cooling. Less than 1 ppm of NO_(x) was detected in the flue gas. The inlet and outlet temperatures of the catalyst bed 250 were about 854° C. and 993° C., respectively. The outside surface temperature of the inner tube 205 was about 662° C.

Two experiments were carried out with the same 1 wt % Pt catalyst under the same operating conditions. Less 9 ppm of CO was detected in the flue gas during both of these experiments, and, therefore, nearly all of the methane was combusted. The CO concentration could be reduced to less than 1 ppm by increasing the length of the catalyst bed to increase residence time.

TABLE 2 Experimental Results for Combustion of Methane in Air Over Combustion Catalysts in a Heat Exchanger-Style Catalyst Tube-Shell Heater Temperature Outlet of Outside Length of Temperature Surface of Air Catalyst of Catalyst Inner Tube Cooling NO_(x) Example Catalyst Bed (in.) Bed (° C.) (° C.) (SCFH) (ppm) 1 4 wt % Pt/3 wt % 1.375 555 to 716 254 to 655 25 to 100 1 to 38 Mg/Al₂O₃ 2 4 wt % Pt/3 wt % 1.375 647 to 678 342 to 523 50 to 65 0 to 6 Mg/Al₂O₃ diluted with inert catalyst carrier material 3 1 wt % Pt/3 wt % 1.5 ~1000 ~662 0 0 to 1 Mg/Al₂O₃

The experimental data indicates that the process for catalytic combustion in a heat exchanger-style catalyst tube-shell heater has an advantage over conventional flame combustion methods in the reduction of NO_(x) formation. The improved catalyst tube-shell heater reduced the NO_(x) concentration in the flue gas to less than about 7 ppm, which is a significant reduction from about the 15 ppm NO_(x) formed for most conventional burners.

Similarly, the improved heat exchanger tube-catalyst-shell heater should reduce NO_(x) concentration in flue gas to less than the NO_(x) formed for most conventional burners.

DEFINITIONS

As used herein, the terms “a,” “an,” “the,” and “said” means one or more.

As used herein, the term “and/or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone; B alone; C alone: A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

As used herein, the terms “comprising,” “comprises,” and “comprise” are open-ended transition terms used to transition from a subject recited before the term to one or elements recited after the term, where the element or elements listed after the transition term are not necessarily the only elements that make up of the subject.

As used herein, the terms “containing,” “contains,” and “contain” have the same open-ended meaning as “comprising,” “comprises,” and “comprise,” provided above.

As used herein, the terms “having,” “has,” and “have” have the same open-ended meaning as “comprising,” “comprises,” and “comprise,” provided above.

As used herein, the terms “including,” “includes,” and “include” have the same open-ended meaning as “comprising,” “comprises,” and “comprise,” provided above.

As used herein, the term “simultaneously” means occurring at the same time or about the same time, including concurrently.

INCORPORATION BY REFERENCE

All patents and patent applications, articles, reports, and other documents cited herein are fully incorporated by reference to the extent they are not inconsistent with this invention. 

1) A process comprising: a) combusting a gaseous volatile organic compound over a modified alumina catalyst at a temperature below 5° C.; b) exothermically producing CO₂ and H₂O at a temperature from about below 5° C. to about 1100° C.; and c) adding a fuel gas to supplement the heat generated from the combustion of the volatile organic compound. 2) The process of claim 1, wherein the modified alumina catalyst comprises from about 0.005 wt % to about 5 wt % Pt. 3) The process of claim 1, wherein the modified alumina catalyst comprises a modified alpha-alumina cloth support. 4) The process of claim 1, wherein the modified alumina catalyst comprises a MgO modified alpha-alumina cloth support or a gamma alumina support. 5) The process of claim 1, wherein NOx is not substantially formed during the production of CO₂ and H₂O. 6) The process of claim 1, wherein the gaseous volatile organic compounds are selected from a group consisting of: methanol, ethanol, propanol, n-heptane, gasoline, crude oil, n-C₁-C₆ paraffins, i-butanol, n-hexane, toluene, acetone, hydrogen and combinations thereof. 7) The process of claim 1, wherein the fuel gas is methane, natural gas or a refinery fuel gas. 8) The process of claim 1, wherein the oxygen containing gas are selected from a group consisting of: oxygen air, oxygen enriched air, nitrogen enriched air or combinations thereof. 9) The process of claim 1, wherein the oxygen content can range from 1% to 100%. 10) A process comprising: a) combusting a gaseous volatile organic compound selected from a group consisting of: methanol, ethanol, propanol, n-heptane, gasoline, crude oil, n-C₁-C₆ paraffins, i-butanol, n-hexane, toluene, acetone, hydrogen and combinations thereof in an oxygen containing gas, over a modified alumina catalyst at a temperature below 5° C. wherein the oxygen containing gas consists of a group selected from: oxygen, air, nitrogen and combinations thereof; b) exothermically producing CO₂ and H₂O at a temperature from about 5° C. to about 1100° C. while not substantially forming NOx; wherein the modified alumina catalyst is comprises from about 0.005 wt % to about 5 wt % Pt and a MgO modified alpha-alumina cloth support or a gamma alumina support; and c) adding a fuel gas to supplement the heat from the combustion of the volatile organic compound. 11) A process comprising: a) using a heat exchanger comprising: i. a heat exchanger; and ii. a thin layer of a modified alumina catalyst bed in contact with the heat exchanger, b) combusting a gaseous volatile organic compound with an oxygen containing gas over the modified alumina catalyst at a temperature below 5° C.; and c) exothermically producing CO₂ and H₂O while simultaneously raising the temperature of the heat exchanger from about 5° C. to about 1100° C. 12) The process of claim 10, wherein the modified alumina catalyst comprises from about 0.005 wt % to about 5 wt % Pt. 13) The process of claim 10, wherein the modified alumina catalyst comprises a modified alpha-alumina cloth support or a gamma alumina support. 14) The process of claim 10, wherein the modified alumina catalyst comprises a MgO modified alpha-alumina cloth support or a gamma alumina support. 15) The process of claim 10, wherein NOx is not substantially formed during the production of CO₂ and H₂O. 16) The process of claim 10, wherein the gaseous volatile organic compounds are selected from a group consisting of: methanol, ethanol, propanol, n-heptane, gasoline, crude oil, n-C₁-C₆ paraffins, i-butanol, n-hexane, toluene, acetone, hydrogen and combinations thereof. 17) The process of claim 10, wherein the oxygen containing gas are selected from a group consisting of: oxygen air, oxygen enriched air, nitrogen enriched air or combinations thereof. 18) The process of claim 10, wherein the oxygen content can range from 1% to 100%. 19) The process of claim 10, wherein the heat exchanger is connected to a preheater or a steam generator. 20) A process comprising: a) using a heat exchanger comprising: i. a heat exchanger; and ii. a thin layer of a modified alumina catalyst bed in contact with the heat exchanger, b) combusting a gaseous volatile organic compound selected from a group consisting of: methanol, ethanol, propanol, n-heptane, gasoline, crude oil, n-C₁-C₆ paraffins, i-butanol, n-hexane, toluene, acetone, hydrogen and combinations thereof in an oxygen containing gas, over the modified alumina catalyst at a temperature below 5° C. wherein the oxygen containing gas are selected from a group consisting of: oxygen, air, nitrogen and combinations thereof; c) adding a fuel gas to supplement the heat from the combustion of the volatile organic compound; d) exothermically producing CO₂ and H₂O at a temperature from about 5° C. to about 1100° C. while not substantially forming NOx; and wherein the modified alumina catalyst is comprises from about 0.005 wt % to about 5 wt % Pt and a MgO modified alpha-alumina cloth support. 